A dramatic change is currently on the horizon in the sector of visual display unit and illumination technology. It will be possible to manufacture flat displays or illuminated surfaces with a thickness of less than 0.5 mm. These are notable for many fascinating properties. For example, it will be possible to achieve illuminated surfaces in the form of wallpaper with very low energy consumption. In addition, color visual display units with hitherto unachievable trueness of color, brightness and viewing angle independence will be producible with low weight and very low power consumption. The visual display units will be configurable as microdisplays or large visual display units of several m2 in area, in rigid or flexible form, or else as transmission or reflection displays. In addition, it will be possible to use simple and inexpensive production processes such as screen printing or inkjet printing or vacuum sublimation. This will enable very inexpensive manufacture compared to conventional flat visual display units. This new technology is based on the principle of OLEDs, Organic Light Emitting Diodes, which is shown schematically and in simplified form in FIG. 36.
Such components consist predominantly of organic layers, as shown schematically and in simplified form in FIG. 36. At a voltage of, for example, 5 V to 10 V, negative electrons pass from a conductive metal layer, for example from an aluminum cathode, into a thin electron conduction layer and migrate in the direction of the positive anode. This consists, for example, of a transparent but electrically conductive thin indium tin oxide layer, from which positive charge carriers, called holes, migrate into an organic hole conduction layer. These holes move in the opposite direction compared to the electrons, specifically toward the negative cathode. In a middle layer, the emitter layer, which likewise consists of an organic material, there are additionally special emitter molecules where, or close to which, the two charge carriers recombine and lead to uncharged but energetically excited states of the emitter molecules. The excited states then release their energy as bright emission of light, for example in a blue, green or red color. White light emission is also achievable. In some cases, it is also possible to dispense with the emitter layer when the emitter molecules are present in the hole or electron conduction layer.
The novel OLED components can be configured with a large area as illumination bodies, or else in exceptionally small form as pixels for displays. A crucial factor for the construction of highly effective OLEDs is the luminous materials used (emitter molecules). These can be implemented in various ways, using purely organic or organometallic molecules, and complexes. It can be shown that the light yield of the OLEDs can be much greater with organometallic substances, called triplet emitters, than for purely organic materials. Due to this property, the further development of the organometallic materials is of high significance. The function of OLEDs has been described very frequently.[i-vi] Using organometallic complexes with high emission quantum yield (transitions including the lowermost triplet states to the singlet ground states), it is possible to achieve a particularly high efficiency of the device. These materials are frequently referred to as triplet emitters or phosphorescent emitters. This has been known for some time.[i-v] For triplet emitters, many property rights have already been applied for and granted.[vii-xix]
Copper complexes of the Cu2X2L4, Cu2X2L′2 and Cu2X2L2L′ form (L=phosphane, amine, imine ligand; L′=bidentate phosphane, imine, amine ligand, see below) are already known in the prior art. They exhibit intense luminescence on excitation with UV light. The luminescence can originate either from an MLCT, CC (cluster centered) or XLCT (halogen-to-ligand charge transfer) state, or a combination thereof. Further details of similar Cu(I) systems can be found in the literature.[xx] In the case of the related [Cu2X2(PPh3)2nap] complex (nap=1,8-naphthyridine, X=Br, I), a transition between the molecular orbital of the {Cu2X2} unit (Cu d and halogen p orbitals) and the π* orbitals of the nap group is discussed.[xxi]

Triplet emitters have great potential for the generation of light in displays (as pixels) and in illuminated surfaces (for example, as luminous wallpaper). Very many triplet emitter materials have already been patented and are now also being used technologically in first devices. The solutions to date have disadvantages and problems, specifically in the following areas:                long-term stability of the emitters in the OLED devices,        thermal stability,        chemical stability to water and oxygen,        availability of important emission colors,        manufacturing reproducibility,        achievability of high efficiency at high current densities,        achievability of very high luminances,        high cost of the emitter materials,        emitter materials are toxic and        syntheses are complex.        
Accordingly, it was an object of the present invention to overcome at least some of the abovementioned disadvantages.